This invention relates to a lost motion drive assembly. The drive is primarily intended for controlling the louvers or doors of the air plenum in an automobile's ventilation system, although other applications are conceivable. Automobiles have an air plenum in which air is heated or cooled and then directed into the passenger compartment through air ducts or vents. These vents are commonly located on the instrument panel, near the floor, and below the windshield for defrosting it. The user selects which vents he wants air to flow from, as well as the air temperature and whether it is recirculated or mixed with outside air. To effect the desired air flow, a plurality of doors or louvers are provided in the air plenum to direct the air through passages to the appropriate vents.
Electric and pneumatic motors have been used for opening and closing the doors, as well as the more economical approach of mechanically connecting the doors to a user-actuatable selector. In the past mechanical switches have involved complicated mechanisms having many parts including cams, followers, levers and the like. The present invention is concerned with a greatly simplified structure providing a mechanical switch for setting the doors in an air plenum.
Modern automobiles provide at least five choices or modes for the air flow. The five modes are panel mode wherein air is directed through vents o the instrument panel; bi-level mode wherein air is directed through both the instrument panel vents and floor vents; floor mode wherein all air is directed through floor vents; air-mix mode wherein outside air is mixed with inside air and is directed through both floor vents and defrost ducts; and defrost mode wherein all air is directed through defrost ducts to the windshield.
One way to make a switch for setting the appropriate plenum louvers to effect each of these modes is to have a separate switch element, such as a lever, for each of the five modes. The present invention provides a switch having only two such levers.